Self-administering a hypodermic medicine injection is a difficult task for many individuals to accomplish. Some individuals experience an aversion to driving a needle into the flesh. The result is that many individuals who have health conditions which require periodic injections or who face an emergency need for self injection, or a need to administer an injection on another human or animal will hesitate or in some instances grow faint at the prospect. At least part of the revulsion may stem from watching the needle penetrate the flesh. Another aspect comes from the act of forcing the needle into the flesh. To many, the aversion is so substantial that they simply refuse to either self inject or to administer an injection to another human or animal.
Thus there is a need for a device that will automatically inject medications without requiring the administering individual to watch the needle penetrate, and without requiring that the individual actually supply the force needed to drive the needle into the flesh and dispense medicine into the recipient.
Various automatic injection apparatus have been previously developed. Such apparatus may be used to self administer or to administer, injections to others, in such a manner that the apparatus only requires triggering. Mechanisms provided within the apparatus automatically drive the needle and dispense the medication. Many prior forms of automatic injectors are single use, although some allow for reloading of hypodermic cartridges in which an ampule is provided with a single, fixed needle that openly communicates with the medication in the ampule.
There is also a need for an automatic form of injector that will accommodate double needle injection cartridges in which two oppositely facing needles are slidably mounted by a hub on a medication ampule. A rearward facing one of the needles is situated adjacent a penetrable seal on the ampule so that forced motion of the syringe assembly will result in the rearward needle piercing the ampule seal and allowing the medication to flow to and out the forward needle. Such action, to be most beneficial, should be accomplished by the automatic injector.
Another need is for an automatic injector that can be adjusted for different penetration depths, from superficial to subcutaneous to intramuscular and deeper penetration depths. This varies according to the condition of the patient and/or the medication being administered. This is not just a need related to automatic injectors, but also for individuals who are unaware of penetration depth requirements.
Need also exists for automatic injectors that can be reloaded with conventional ampules to allow for administration of multiple doses. Such injectors allow for removal and replacement of the ampules and re-use of the injector mechanism. Another mode of use is as a single ampule for one injection to give a first dose, and then to reset the injector for a second injection from the same ampule for a second or other multiple doses.
Another pertinent need is the ability to remove the syringe subassembly from the injection device. This may be needed when the injection device malfunctions or when immediate administration of a second or subsequent dose is required.
Some or all of the above needs and others are addressed in part or fully met by various embodiments of the present invention as described below.